Thermostat



April 28, 1931. H, DORFMAN 1,802,758

THERMOSTAT Filed Aug. 6, 1929 Fig. .1.

INVENTOR ATTORNEY Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE HIILER I). DORFMAN, OF MANSFIELD, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA THERMOSTAT Application filed August 6, 1929. Serial No. 383,928.

My invention relates to snap-acting circuit breakers or switches and particularly to thermostatic latching means therefor.

An object of my invention is to provlde a relatively simple, compact, inexpensive and quickly-operative thermally-actuable c urrent-traversed latch for a snap-acting switch.

In practicing my invention, I provide, in

combination with a snap-acting switch embodying a toggle, a thermostatic latch, 1ncluding a bimetalliccurrent-traversed member of substantially U-shape, terminal plates of L-shape being secured to the ends of the leg portions of the member of U-shape. A

latching structure is secured to the mtermediateportion of the bimetallic member of U-shape, integral longitudinally-extending lugs being provided thereon, metallic plates being insulatedly secured thereto by rivets extending through the perforated lugs.

In the single sheet of drawings:

Figure 1 is a view, partially 1n side elevation and partially in section, of a toggle snapacting switch with which is associated a thermostatic latch embodying my invention Fig. 2 is a View, in front elevation, of a thermostatic latch embodying my invention;

Fig. 3 is a view, in IongItudinal section, taken on the line III-III of Fig. 2; and

Fig. 4 is a view, in lateral section, taken on. the line IV-IV of Fig. 2.

Referring first to' the switch structure, I have illustrated a base plate 11 which may be made of suitable electric-insulating material and is provided with a recess 12 in its upper face to receive the switch structure.

A mounting bracket 13 is of substantially U-shape in lateral section, having an arm.14 on one side thereof and having two arm portions 16 and 17 on the other side thereof, together with an intermediate portion which is secured, by mounting bolts (not shown), against the upper face of the member. 11 in the recess 12.

A cradle 18 comprises an arm 19 which is substantially straight and a second arm 21 which is of substantially inverted U-shape', together with an intermediate portion 22. The cradle 18 is of substantially U-shape, the

arm portions thereof being, however, not in' alignment with each other, and is pivotally mounted on the mounting plate 13 by a pin or shaft 23 extending through the arms 19 and 21 closely adjacent to the intermediate portion 22. I

A resilient contact arm 24 has one end thereof secured to the intermediate portion of a bracket member 26, of substantially U- shape, which is, in turn, pivotally mounted on a pin 27 supported by the mounting plate 13. The outer end of the arm 24 has mounted thereon a contact member 28 which is adapted to engage, and be disengaged from, a stationary contact terminal 29 suitably secured to the upper face of the base plate 11.

A flexible conductor 31 provides an electrical connection between the inner end of the arm 24 and a fixed contact terminal 32 which is mounted within the recess 12 of the base plate 11.

Means for actuating the contact arm comprises a handle arm 33, of inverted U-shape, which has secured thereto a cover member 34 of arouate shape embodying an actuating knob or handle 36. The arcuate member 34 is suitably secured, as b rivets or screws, 2% the intermediate portion of the member The outer ends of the arms of the member 33 are provided with apertures and are pivotally mounted on a pin or shaft 37 which is supported by the portion 14 of the mounting bracket 13.

A toggle is provided which comprises an upper arm 38 and a lower arm 39 pivotally connected by a pin 41. The upper end of the arm 38 fits pivotally within the bend ofthe arm 21 which, as was hereinbefore described, is of substantially inverted U-shape. The lower end of the toggle arm 39 is mounted on a shaft 42 which is, in turn, mounted on the bracket 26 in such manner that the relative positions of the arm 39 and of the bearing bracket 26 may be varied. While I have described the toggle as comprising single arms, I may use two arm portions for either or both of the arms, and one or a plurality of springs 43 are provided, the ends of which are connected, respectively, to

the pin or shaft 41 and the intermediate portion of the arm 33.

The details hereinbefore described are not essential to the present invention but have been illustrated and describedms a suitable snap-acting switch with which the device now to be described may cooperate.

In Figs. 2, 3 and 4, I have illustrated a bimetallic element 51, of inverted U-shape, its

leg portions being of varying widths from a minimum adjacent to their outer or lower ends to a maximum at their upper or inner ends, where they are integrally united by a body portion having integral lugs 52, each of which is perforated.

Terminal plates 53, each of substantially L-shape, are secured, by rivets 54, to the perforated outer ends of the legs of the bimetallic member 51.

A. latch structure is secured to, and insulatedly mounted on, the body part of the member 51 and more particularly to the lugs 52, and comprises a metal plate 56, a plate 57 of electric-insulating material located between the faces of the lugs 52 and the plate 56, a second plate 58 of electric-insulating material and a second metallic plate 59 on the other side of the plate 58. Rivets 61 and 62 extend through the plates 56 to 59, inclusive, and through the lugs 52 in order to hold all of these parts in tightly assembled relation, substantially as shown in the drawing.

Plate 56 is provided with a substantially central elongated aperture 63, and plate 59 has a struck-out portion 64 which extends between the lugs 52 andthrough the opening 63, in substantially the manner shown in Figs. 2 and 3 of the drawing, to cooperate with the outer end of the arm 21 of the cradle 18.

It is to be understood that the bimetallic member 51 is connected in series electrical circuit with the switch hereinbefore described and in electrical series with the circuit which the switch is to control. The details of these connections are omitted in order to simplify the drawing.

A cover 66 is provided for the switch, and a plurality of arcing plates 67 are shown, all of which have been more clearly described and claimed in a copending application filed April 20, 1929, Serial No. 356 646, by O. S. Jennings and assigned to the Westimghouse Electric and Manufacturing Company.

The respective parts of the switch are shown in Fig. 1 of the drawing in an intermediate stage of operation where the outer end of arm 21 of the cradle has been caused to engage with the latch structure and, more particularly, the struck-out portion 64. This is effected by moving the knob 36 toward the left, as shown in the drawing. To close the switch, the arm 36 is moved toward the right whereby the upper end of thetoggle spring 43 is also moved to the right to tension the spring, the toggle joint pin 41 being also in the arm 21. Hence, the lower part of the lower toggle arm 39 will be moved downwardly around the pivot pin 27 to carry the contact arm 24 and the contact member 28 downwardly. Upon continued turning movement of the knob 36 and the member 33 to the right, as just described, the contact member 28 will finally engage the fixed contact member 29 and, when this has been effected, the pin 41 will be located on the other side of a line joining the center of the pin 37 and the connecting point of the upper end of the spring 43 in member 33, with the result that the toggle is blocked and the contact members are in engagement.

If now, the circuit, the switch and particularly the bimetallic member 51 are traversed by an abnormally high current for a predetermined length of time, the bimetallic member 51 will be caused to move the upper end thereof to the left, as shown in the drawings, to release the latching structure from engagement with the outer end of the arm 21. it is, of course, to be understood that the time to effect this disengagement decreases with an increase in the value of the current traversing the member 51. It has been found in actual practice that the movement of the free end of the member 51 is almost instantaneous in the case of a very heavy current traversing the switch and the bimetallic memher, as will happen in the case of a short circuit in the line. I

Upon release of the cradle, it will have a turning movement to the right, whereby the toggle joint is permitted to open, and the contact members will then be disengaged, thereby opening the circuit. To reclose the switch, the knob 36 is first moved to the left to cause engagement of the latching structure and the cradle and then the knob is moved to the right, in the manner clearly set forth in the hereinbcfore mentioned'copending application.

By providing the minimum area of currentconducting bimetallic material closely adjacent to the fixed support thereof, I am able to obtain a maximum degree of bending or turning movement of the-latching structure secured to the free end of the bimetallic latch so that the quickest possible disengaging movement of the latch is obtained in response to abnormally large current values traversing the circuit and the bimetallic member.

The thermally-actuable latch provides further a very simple structure embodying metal plates insulatedly secured to the intermediate portion of a bimetallic member of U-shape and particularly interfitting the metallic plates or portions whereby a relatively strong and rigid lat-eh structure is obtained. lhe assembly of the plates 56 and 59 on the member 51 is shown in Fig. 3 of the drawings and it may be noted that the upper surface of the portion 64 is in close operative engagement with the wall of the opening 63 and particularly with'the upper wall portion and is spaced from the lower wall of the opening 63. I y

The device embodying m invention thus provides a relatively s1mp e, compact and easily assembled and installed thermostatic latch for a snap-acting switch.

Various modifications may be. made in the deviceembodying my invention without departing from the spirit and scope thereof and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. A thermally-actuable latch for holding a snap-acting switch in its closed'position, said latch including a current-traversed bimetallic member of substantially U-shape, the legs thereof decreasing in width towards their free ends and having a body provided with perforated lugs, current-conducting supporting angle-bar members secured to the free ends of the legs of said bimetallic memher and a latching lug for said switch insulatedly mounted on said perforated lugs.

2. A thermally-actuable latch for holding a snap-acting switch in its closed position, said latch including a current-traversed bimetallic member of substantially U-shape and including a perforated plate located ad- 'acent to one face of the bod portion of said imetallic member, a secon plate having a struck-out portion extending through the perforation in the first plate andmeans for securing said plates together and to said bimetallic member.

3. A thermally-actuable means for holding a snap-acting switch in its closed position, said holding means including a current-traversed bimetallic member of substantially U-shape, the width of thelegs of said member decreasin towards the free ends thereof and the b0 y portion being provided with perforated extensions longitudinally alined with the legs, terminal members of L-shape secured to the ends of the legs of the bimetallic member, a centrally-perforated metal plate located adjacent to one face of the perforated extensions, a second metal late, having a struck-out portion extending aterally of its surface and through the aper ture in the first plate to directly engage said switch, and means extending through said plates and said perforated extensions for securing said plates on the bimetallic member.

4. thermally-actuable means for holding a snap-acting biased switch in its closed position, said means including a bimetallic member having a non-current-traversed portion and an integral current-traversed por- 

